It is known to use a butterfly type valve to control the flow of air into an internal combustion engine. It will be appreciated that the term ‘air’ as meant herein includes not only atmospheric air admitted via an air inlet but also other gas flows to the engine such as, for example, recirculated exhaust gas and crankcase ventilation gas.
It is a problem with such a butterfly arrangement that when the butterfly valve is in a partially open position considerable downstream turbulence is produced which has an adverse effect on engine efficiency. Even at wide open throttle there will be a pressure drop and turbulence from the throttle plate of a butterfly type valve.
It is an object of this invention to provide a more efficient type of throttle valve.
According to a first aspect of the invention there is provided a throttle valve assembly comprising a throttle body defining a quadrilateral shaped air flow passage and a throttle valve mounted in the air flow passage of the throttle body wherein the throttle valve comprises first and second interacting throttle plates configurable to produce a convergent/divergent flow restricting configuration when a reduced flow of air through the throttle body is required and into a flat minimally intrusive flow restricting configuration when no reduction in the flow of air through the throttle body is required wherein the first throttle plate is positioned upstream from the second throttle plate and forms the convergent part of the convergent/divergent flow restricting configuration and the second throttle plate forms the divergent part of the convergent/divergent flow restricting configuration.
The assembly may further comprise an actuator and the first and second throttle plates are configurable by the actuator to produce the convergent/divergent flow restricting configuration when a reduced flow of air through the throttle body is required and into the flat minimally intrusive flow restricting configuration when no reduction in the flow of air through the throttle body is required.
The first throttle plate may be rotatable about one end by the actuator and the second throttle plate may be rotatable by the interaction of the second throttle plate with the first throttle plate.
The quadrilateral air flow passage may be defined by an upper wall of the throttle body, a lower wall of the throttle body and two side walls of the throttle body and the first throttle plate may be pivotally connected to the upper wall of the throttle body.
The second throttle plate may be rotatably connected to the upper wall of the throttle body and may interact with the first throttle plate via a sliding interaction of a free end of the second throttle plate with a rear face of the first throttle plate.
In the flat minimally intrusive flow restricting configuration the first and second throttle plates may lie upon one another against an inner surface of the upper wall of the throttle body. Alternatively, the second throttle plate may interact with the first throttle plate via a pivotal connection and may have a free end slidingly abutting an inner surface of the upper wall of the throttle body.
In which case, in the flat minimally intrusive flow restricting configuration, the first and second throttle plates may lie end to end against the inner surface of the upper wall of the throttle body.
According to a second aspect of the invention there is provided an engine air induction control system for a motor vehicle comprising an air flow path to an engine including a throttle valve assembly constructed in accordance with said first aspect of the invention, an electronic controller, an accelerator pedal position sensor associated with an accelerator pedal of the motor vehicle to provide a driver torque demand input to the electronic controller and an electronically controllable actuator forming part of the throttle valve assembly operably connected to the electronic controller.
The electronic controller may be arranged to operate the electronically controllable actuator to move the throttle valve based upon the driver demand input from the accelerator pedal position sensor.
The electronic controller may be operable to use the electronically controllable actuator to move the throttle valve of the throttle valve assembly to increase the air flow area of the throttle body from the current air flow area if the input from the accelerator pedal position sensor indicates a request for increased engine torque.
The electronic controller may be operable to use the electronically controllable actuator to move the throttle valve of the throttle valve assembly to reduce the air flow area of the throttle body from the current air flow area if the input from the accelerator pedal position sensor indicates a request for reduced engine torque.
According to a third aspect of the invention there is provided a motor vehicle having an internal combustion engine and an engine air induction control system constructed in accordance with said second aspect of the invention.
With reference to FIG. 1 there is shown a motor vehicle 5 having a direct injection gasoline engine 10.